Guppy VS Guppy: Aggressive behavior?

Question

I have been starting a new tank for about 3 weeks now so my nitrate cycle is about half way complete. I understand that the few fish that I put in there will most likely die because of this. However, my "test guppies" are highly aggressive to each other. I put three in the tank, one of which stressed out and died and the other two are still alive. The one young female guppy is completely beating up the older and very pregnant guppy. Her tail has almost completely been ripped apart over the last 4 days. This is the second batch of 3 guppies I have put in to the tank (of course the first three died) and the same thing happened with those guppies.

My friend says it's all about territory. I have a 10g with 4 plants that are 3-4 inches high but no tall plants. He says I need 4 or 5 tall fake plants to put in there so they can hide/play/define territory from each other.

I feel like they're aggressive because the tank has not completed it's cycle and the water is unstable leading to high stress.

Should I be concerned with this high level of aggressiveness?

Anonymous · Accepted Answer

I've kept guppies for a while now, and I've never come across aggression like that!!!!! Try putting in more fake plants, see if that calms the aggression a little. My tanks have tons and tons of Java Moss too, so maybe try that. You could also try adding a male to keep the non pregnant girl occupied, he will chase her around a lot. 
Could your guppies be getting cut up from your decoration? Or could they possibly be suffering from fin rot? You said your tank is cycling, that can lead to a higher chance of fish getting diseases. 
I always have used guppies to cycle tanks. Usually, as long as you're doing daily water changes, you should have no trouble keeping your fish alive. Three guppies really shouldn't be too much of a bio load for a ten gallon tank. 
Best of luck with your fish and tank, and hopefully you can sort out that aggressive guppy!!

Anonymous · Answer

The difference is in the breeding. Theoretically, the fancy guppies have been selectively bred to have certain characteristics--the tail shape, the coloring, the patterning (snakeskin, tiger strips, etc.), which is why they cost more. Feeder guppies are just mutts--they've mated with any other guppy so there is no way (so far) to trace what their genetic lines are so you can't predict what their offspring will be like (breeding true to a certain characteristic). Like puppy mills, feeder guppies are often kept in substandard conditions and are allowed to breed indiscriminately and often so they produce a lot of babies whether the fish are healthy or not (abnormal guppies are allowed to breed since the fish are only going to be fed to bigger fish). Feeder guppies will have colors and long fins too, just nothing you can predict if you were to mate it to a female just like it since it's genes are a jumble of different donors. Even fancy guppies will sometimes throw the oddball weirdo offspring (stunted or with disfunctional fins or a crooked spine etc. that should not be bred ever).

lynne r · Answer

I've never done cycling with fish as it's unnecessary stress for them and they often die. Some female guppies can be aggressive but are you sure she's a guppy and not a Mosquito fish? http://www.dkimages.com/discover/previews/810/95007021.JPG
they are sometimes sold in with guppies by mistake and are very aggressive-what colour is your female?

Anonymous · Answer

Well, first of all, you should not be using "test guppies", as that is cruel. Second of all, yes, you should be concerned. If you are very against doing a fishless cycle, then I advise you to take out the hurt and pregnant guppy, and let the other one be the one to be the tester. You should not just let her die, especially because she is pregnant, and also injured.

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Guppy VS Guppy: Aggressive behavior?

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